The overall goal of the proposed research is to use nationally representative health interview survey data, the 2004 wave of the Health and Retirement Study (HRS), to investigate frailty in older adults. Using physical performance measures newly available in the HRS, the research will operationalize the frailty phenotype developed by Fried et al. The research will then compare the Fried model to other models of frailty; examine the association of frailty with other defining clinical characteristics of older adults (multimorbidity, cognitive impairment, disability); and examine utilization patterns and cost outcomes associated with these characteristics. The proposed research will evaluate three hypotheses: (1) the prevalence of frailty in the HRS is similar to that in the Cardiovascular Health Study (CHS), the population sample in which the Fried frailty phenotype was first operationalized. (2) Self-report measures may substitute for performance measures as frailty-defining criteria. (3) Although the frail population overlaps with populations with multimorbidity and with disability, nonetheless, the three are distinct, with distinct health care utilization patterns and costs. The proposed research will be an initial step to a more comprehensive study that will incorporate linked Medicare claims data and longitudinal survey data. [unreadable] [unreadable]